Reference is made to sorting systems where the code is attached to an object and by which the object can be identified as it moves past an inspection station. For example, railroad car identifying patents such as U.S. Pat. Nos. 3,277,283 and 3,304,412 show optically read "labels" that enables a freight car to be identified as it moves. U.S. Pat. No. 3,739,181 shows an arrangement for coding objects where tabs carrying coded messages are magnetized in a special manner and the magnetic codes can be detected by suitable devices. These magnetic tabs act as an escort memory for the objects being transported.
U.S. Pat. No. 3,784,795 shows a label to be attached to packages where said label is then read by optical means. U.S. Pat. No. 3,309,771 describes a magnetic stripe that can be printed on an envelope or on other pieces of mail and which can be read by a magnetic pickup head as a piece of mail passes it. U.S. Pat. No. 3,662,181 describes a bar code which is printed on an object and which can be optically detected and read as an object moves past a detection station.
A very widely used coding scheme is the Universal Product Code, more familiarly known as the UPC code, which can be seen on objects such as those in a grocery store. The codes are read by a laser scanner at the checkout counters. Such bar codes are now becoming widely used on such things as magazine covers and many other objects which have to be checked or sorted sometime during their life time. Please note that in the systems mentioned so far the code is either attached to an object or is part of the object itself and is not easily changed in transit as is required in a system such as for letter sorting. When it is desired to change a code "on the fly" and not attach the code to the object itself, such as in the case of letters or postal cards, escort memories have been resorted to. U.S. Pat. No. 2,961,093 was issued to me in connection with the sortation of punch cards. Here, a binary code, consisting of settable cams, carries the information along with each card. The cams can be easily set and reset as described in the patent.
Coming closer to the matter of this patent application, note particularly conveyors such as used for letter mail described, for example, in U.S. Pat. No. 2,901,089 issued to Lawrence J. Kamm and to me dated Aug. 25, 1959. See also U.S. Pat. No. 3,538,338, issued to me on Nov. 3, 1970, which shows another type of optical escort memory, and my U.S. Pat. No. 4,194,126 on still another escort memory. Reference is also made to U.S. Pat. No. 3,080,985, which shows a method for setting the code wheels of the above-mentioned U.S. Pat. No. 2,901,089. An additional patent of interest may be U.S. Pat. No. 4,022,340, issued to Andrew E'Aloia on May 10, 1977, which shows a modification of the letter carrier system first disclosed in my U.S. Pat. No. 2,901,089.
Escort memories may be of many types--mechanical memories, such as shown in the referenced patents referred to above; optical memory, such as shown in U.S. Pat. No. 3,358,338, mentioned above; magnetic recordings either carried by the conveyor belt or by members attached thereto; and so on.
The present invention is intended to overcome many of the problems experienced by prior art devices. The device of Patent '089 issued to Lawrence Kamm and myself describes a code memory in widespread use today in the United States Post Offices. The mechanical code wheels produce a great deal of noise and require a considerable amount of servicing. Moreover, the mechanism to set and reset the codes is quite elaborate and is also subject to a considerable number of mechanical problems. U.S. Pat. No. 3,538,338 shows an optical memory which does not produce noise but which requires mechanical setting and resetting the codes and recognition of the code by the code detector. With the normal operation of conveyor belts such as used in Post Offices, the mechanical tolerances become very difficult and damage to the optical components can easily occur.
U.S. Pat. No. 4,194,126 shows another optical memory consisting of a series of mirrors. This invention avoids some of the problems enumerated above but still requires mechanical setting and resetting of the mirrors with attendant wear and requirement of high precision in the position of the mirrors.